On my Windows machine -- I typically test different versions of Internet Explorer using an array of Virtual Machine instances (which obviously requires a fair amount of investme
Recently (January 2013) Microsoft released a website called http://www.modern.ie/ to deal with testing with different versions of IE, even on different OSes.
It is based on having different VMs targeting the enviroment you want to test (e.g. IE8 on Win7), so you need to choose the type of OS and Virtualization Platform you want to use and then download the VM image.
It seems to be a lot more reliable that IE collection as you are testing the full browser stack.